1. Technical Field
This disclosure generally relates to parallel computer systems, and more specifically relates to timestamp synchronization for queries to database portions in nodes that have independent clocks in parallel computer systems.
2. Background Art
Database systems are well-known, and allow queries to be executed to retrieve data from one or more database tables. A query language such as Structured Query Language (SQL) is typically used to write database queries. It is often useful to include a timestamp parameter in a query so the database system can identify exactly when the query was executed. When executing an SQL query to database portions that have a common clock, the timestamps will all be based on the common clock and will therefore be consistent. However, many parallel computer systems include multiple nodes that each have an independent clock. When a query references different database portions that have independent clocks, the timestamp value for one portion will not necessarily match the timestamp value for the same query on a different portion that has a different clock. Without a way to synchronize the timestamp parameters in different nodes that execute a common query in a parallel computer system, the timestamp parameter will have limited value due to the potential differences between timestamps for different portions of the same query.